137Cs elimination by chronically-contaminated largemouth bass (Micropterus salmoides)

The temperature-dependent 137Cs biological half-times (Tb) of lifetime-exposed largemouth bass (Micropterus salmoides) from a nuclear cooling reservoir at the U.S. Department of Energy's Savannah River Site were calculated from whole-body measurements of live fish and compared with literature records for acutely and chronically-contaminated fish. The Tb's of the bass averaged 322 d (95% CI: 311-333 d), 225 d (95% CI: 220 to 230 d), and 140 d (95% CI: 137 to 143 d) at 15, 20, and 26 degrees C, respectively. These mean Tb's were 1.7 to 2.5 times longer than would be expected for acutely contaminated fish, and 1.2 to 1.8 times longer than those predicted for fish at steady-state with their environment according to recent models. This slower elimination did not appear to result from slower elimination from skeletal muscle compared with other soft tissues, in that the muscle to whole-body 137Cs concentration ratios after the elimination period were similar to those of freshly-caught bass. Our results suggested that elimination rates estimated from the terminal elimination components of acutely-dosed fish may not reflect the elimination rates of fish exposed to contaminants throughout their lifetime, even when care is taken to allow sufficient time for absorption of the dose.